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Yoon Publishes on Titan’s Haze

Posted on Thursday, May 08, 2014

Y. Heidi Yoon, a visiting assistant professor of chemistry, has had an article published in the journal Icarus. Titled, "The role of benzene photolysis in Titan haze formation," the article is based on research she conducted at the University of Colorado, Boulder, where she was previously a postdoctoral associate at the Cooperative Institute for Research in Environmental Sciences.

As part of the joint NASA/European Space Agency Cassini mission, the Cassini spacecraft has been orbiting and collecting data about Saturn and its moons since 2004. During this mission, the presence of benzene has been confirmed at sub-parts per billion to parts per million levels in the atmosphere of Titan, the largest moon of Saturn.

"The confirmation of benzene is important, since it may be the molecular precursor for haze formation in Titan's atmosphere," says Yoon.

To understand the role of benzene photochemistry in haze formation, Yoon and colleagues simulated Titan's atmosphere in the laboratory. Using a gas mixture close to that in Titan's atmosphere, they flowed their gas mixture into a reaction chamber that is irradiated by a deuterium lamp.

"The lamp models the solar spectrum and initiates photochemistry like that in Titan's atmosphere. Using mass spectrometry techniques, the product gases and aerosol particles are sampled and we find with benzene addition that the level of unsaturation in the products is increased," explains Yoon.

She notes significant amounts of benzene may also be important for the optical properties of Titan's haze atmosphere. Since benzene may grow into larger aromatic structures, its conjugated system can readily absorb in the visible and UV. The abundance of aromatic structures may control the optical properties of the haze and directly affect the thermal structure of the atmosphere.

These results are explained in this latest article, as well as in a previous work in which Yoon was also a coauthor, "The Influence of Benzene as a Trace Reactant in Titan Aerosol Analogs." Ap. J. 766, L4 (2013). Yoon has also presented this work at the 246th American Chemical Society National Meeting in 2013.

Yoon joined faculty in 2013 and is interested in studying photochemistry in planetary atmospheres. She earned her S.B. from the University of Chicago and her Ph.D. from the University of Wisconsin.